Experimental Study of Nonlinear Interface between Glass and Liquid Crystal

The reflection at a nonlinear interface between glass and liquid crystals (MBBA) in their isotropic liquid phase or in the nematic mesophase have been investigated. For some of these studies, a Q-switched ruby laser of pulse duration ~25 nsec was used as a light source. The liquid-crystal cell (48 mm × 18 mm) was constructed of BaF5 optical glass with the liquid crystal forming a layer of 300-μm thickness. The experimental cell temperature was controlled by an oven to an accuracy of ±0.02°C. At the ruby frequency (λ = 694.3 nm) the difference in the refractive index between the glass used and MBBA is Δn = 1.5 × 10−3, thus the critical angle for total internal reflection (TIR) is θc = 87.5° (or ψc = 90° – θc = 2.5°).